A large unexploded bomb from World War II discovered in the Polish city of Wroclaw forced the evacuation of 2,500 residents on Friday.

The bomb weighing 550 pounds was found near a railway overpass in the city in southwestern Poland during construction work.

Poland's armed forces said it was a German SC-250 aerial bomb from the war.

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The city organized buses to take the evacuated residents to a safe area while bomb removal experts worked at the scene. Train traffic also had to be halted until the bomb was removed, according to Polish media reports.

Police spokesperson Aleksandra Freus told broadcaster TVN24 that not all residents agreed to leave their homes and that authorities could not force them to do so. Police issued a public call to evacuate, citing "the threat to human health and life caused by unexploded ordnance."

During World War II, Wroclaw was the German city of Breslau. It saw heavy fighting and widespread destruction, coming under heavy Soviet bombardment before Germany's surrender.

The city became part of Poland when borders were redrawn after the war, with the defeated Germany forced to give up territory.